1. Field of the Invention
The present invention relates to a multilayer ceramic capacitor to be embedded in a board, a method of manufacturing the same, and a method of manufacturing a board having a multilayer ceramic capacitor embedded therein.
2. Description of the Related Art
A multilayer ceramic capacitor (MLCC), a multilayer chip electronic component, is a chip-type condenser mounted on printed circuit boards of various electronic products including display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), and the like, computers, personal digital assistants (PDAs), cellular phones, and the like, to charge and discharge electricity.
Multilayer ceramic capacitors (MLCCs) may be used as components of various electronic devices due to advantages thereof such as a small size, high capacitance, ease of mounting, and the like.
Recently, as the performance of portable smart devices such as smartphones, tablet personal computers (PCs), or the like, has improved, a driving speed of an application processor (AP) used for calculations has increased. When the driving speed of the AP is increased as described above, high frequency current should be rapidly supplied to the AP.
The multilayer ceramic capacitor serves to supply current to the AP. Therefore, in order to rapidly supply the high frequency current as described above, a multilayer ceramic capacitor having low equivalent series inductance (ESL) should be used or a multilayer ceramic capacitor should be embedded in a board to maximally decrease a distance between the multilayer ceramic capacitor and the AP.
In the former case in which a low ESL multilayer ceramic capacitor is used, a structural problem may occur. Therefore, recently, research into the latter case in which the multilayer ceramic capacitor is embedded in the board has been actively conducted.
In the multilayer ceramic capacitor to be embedded in the board, a metal layer mainly formed of copper (Cu) is formed on a surface of an external electrode.
After the multilayer ceramic capacitor is embedded in the board, the metal layer serves to electrically connect a circuit on the board to the multilayer ceramic capacitor by a via hole process using a laser beam and a plating process of filling the via hole with copper.
After the multilayer ceramic capacitor is embedded in the board, the via hole is formed by penetrating through a resin layer using the laser beam so that the external electrode of the multilayer ceramic capacitor is exposed, and the via hole is filled with copper by the plating process so that an external wiring and the external electrode of the multilayer ceramic capacitor are electrically connected to each other.
In this case, the laser beam may be absorbed due to a glass component in the external electrode while penetrating through a plating layer of the multilayer ceramic capacitor, thereby directly damaging a ceramic body. Therefore, the plating layer should be thick, and the external electrode should have a uniform thickness and a flat surface.
When the thickness of the external electrode is not uniform and the surface of the external electrode is not flat, scattered reflections of the laser beam may be generated on a surface of the plating layer to cause damage to a resin portion around the plating layer. Therefore, an inner portion of the via hole may be non-uniformly plated at the time of performing the plating process to cause cracking, or the like, in a via electrode.
Meanwhile, when a space is generated between a chip and an epoxy layer after a built-up film is attached and compressed, delamination may be generated. Therefore, it is important to closely bond the built-up film to the chip.
In addition, the ceramic body and the external electrode of the multilayer ceramic capacitor may have a step therebetween, generated by a thickness of the external electrode. In this case, when the step is excessively large, a space between the multilayer ceramic capacitor and the built-up film is increased, so that the possibility of delamination is increased.
Therefore, in order to decrease the delamination, the thickness of the external electrode or the thickness of the plating layer is decreased. In this case, the ceramic body may be damaged during laser processing, and thus, there has been a limitation in decreasing the thickness of the external electrode or the thickness of the plating layer.
Therefore, in order to decrease the delamination due to the step between the external electrode and the ceramic body, the thickness of the external electrode may be gradually decreased in order not to form a steep step at a distal end portion of the external electrode.
The multilayer ceramic capacitor to be embedded in the board is thinner than the multilayer ceramic capacitor which is not to be embedded in the board, but is to be mounted thereon. In the case of the multilayer ceramic capacitor to be embedded in the board, when a thickness of the ceramic body is excessively thin, a paste is thinly applied to an exposed surface of an internal electrode, such that the external electrode is formed. Therefore, high temperature reliability may be degraded due to permeation of a plating solution.
In addition, when viscosity of the external electrode is increased in order to increase a thickness of the exposed surface of the internal electrode, a band surface may be increased in terms of thickness, such that a flatness of the band surface is decreased and an angle of a distal end portion is increased, thereby causing the above-mentioned cracking in the via electrode or delamination.
The following Patent Document 1 includes a ceramic body, an external electrode, and a plating layer, and does not specifically limit numerical values with respect to a flatness of the plating layer.